Is this the End of Summer?

It was in the 90s on Monday, the 70s on Tuesday, and today it struggled to reach 60.  Quite a marked change.  After a fall-like weather system at the end of August, you may be wondering if summer is over.

Traditionally, summer in the Inland NW is defined as 4th of July to Labor Day.  

Here's the normal (brown shading) and extreme (red for highs, blue for lows) for Deer Park, WA throughout the year.  On average, the hottest days of the year span from 22 July - 6 August, when the average high temperature is 87F.  By the 2nd of September, the average high has dipped back down below 80F with an average low of 43F.  That similar to the normal temperatures for late June. 


The big difference between late June and early September is the length of day.  For June 30, sunrise is at 454am and sunset is 852pm, for a day length of 16 hours.  By September 2nd, sunrise is 610am and sunset is 730pm, so the day length is now only 12 hours 20 minutes.  That's a big difference.  

So back to our original question:  is summer over?  For the next 10 days, we don't see any hot weather.  We'll warm back into the lower 80s by this coming weekend, but then we go back to the 70s next week.  The folks at the Climate Prediction Center show that all the hot and dry weather will be over the central part of the US next week.




That pattern sure doesn't look very summer-like for our area.  What about beyond that?  CPC also has a new Week 3-4 outlook.  Here's what there latest thoughts are for that period.  Yes, they see a little wedge of above-normal temperatures for western Washington, but in general they expect the hot weather to stay over south-central US, where it's been most of this summer.





Also note that they expect the middle two weeks of September to be on wetter side.




Could we still see a few days above 90F?  Sure.  An average September will see two such days. There were seven 90+F days in 2011. But day length is getting so markedly shorter by mid September (sunset is 7pm), the 90F temperatures only last a couple of hours.

Looking a little closer at the next week of weather, there is another Pacific system heading into the Northwest on Thursday.  But this system will get stretched apart and won't give us much more than sprinkles.  Skies will be cloudy so temperatures will once again be in the 60s.  

Temperatures will warm into the lower 80s for Friday-Sunday with a small chance of showers.

For next week, temperatures will drop back into the 70s as another Pacific system arrives with some light rain.  After that drier air with moving into the region.  We'll have to keep an eye on this.  With dew points in the lower 40s, frost is a possibility.



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